MESOSCALE DISCUSSION 1922
NWS STORM PREDICTION CENTER NORMAN OK
0824 PM CDT FRI SEP 07 2012
AREAS AFFECTED...AR/FAR SOUTHEAST MO/SOUTHERN IL/WESTERN KY TO
WESTERN TN AND NORTHERN MS
CONCERNING...SEVERE THUNDERSTORM WATCH 630...632...
VALID 080124Z - 080300Z
THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH
630...632...CONTINUES.
SUMMARY...DAMAGING WINDS WILL REMAIN A CONCERN INTO LATE EVENING
WITH AN EXTENSIVE SQUALL LINE FROM SOUTHERN IL/FAR SOUTHEAST MO AND
CENTRAL/NORTHEAST AR INTO WESTERN/CENTRAL KY...WESTERN/MIDDLE
TN...AND NORTHERN MS. SEVERE THREAT CONTINUES TO QUICKLY WANE ACROSS
SEVERE TSTM WATCH 630...WHILE CONTINUING ACROSS 632 UNTIL 05Z...WITH
NEWLY ISSUED WATCH 633 TO THE EAST OF WW 632 /UNTIL 07Z/.
DISCUSSION...SOUTHWESTERN HALF OF A 500-MILE EXTENSIVE SQUALL LINE
EXTENDS FROM THE WABASH/LOWER OH RIVER VICINITIES OF SOUTHWEST
INDIANA/SOUTHERN IL AND FAR SOUTHEAST MO/FAR WESTERN KY
SOUTHWESTWARD TO NEAR I-40 IN AR/JUST NORTH OF LITTLE ROCK AS OF
0115Z. A DEGREE OF COOLING HAS OCCURRED POST-SUNSET WELL AHEAD OF
THE SQUALL LINE...BUT THE PRE-COLD FRONTAL/SQUALL LINE AIRMASS
NONETHELESS REMAINS MOIST /UPPER 60S TO LOWER 70S F SURFACE
DEWPOINTS/ AND MODERATELY UNSTABLE. THIS IS ESPECIALLY THE CASE
ACROSS MUCH OF KY/FAR NORTHEAST AR INTO TN WITH BOUNDARY LAYER
ADJUSTED 00Z OBSERVED SOUNDINGS FROM LITTLE ROCK AND NASHVILLE
INDICATIVE OF AS MUCH AS 2000-2500 J/KG MLCAPE.
WHILE THE BOUNDARY LAYER WILL CONTINUE TO COOL AND CINH WILL
GRADUALLY INCREASE WITH TIME...THE ORGANIZED NATURE OF THE SQUALL
LINE AND AMPLE VERTICAL SHEAR/LARGE SCALE ASCENT WILL HELP MAINTAIN
A DAMAGING WIND THREAT SOUTHEASTWARD INTO EASTERN AR AND
WESTERN/CENTRAL KY AS WELL WESTERN/MIDDLE TN...AND EVENTUALLY
NORTHERN MS/PERHAPS FAR NORTHERN AL THROUGH LATE EVENING/EARLY IN
THE OVERNIGHT. THAT SAID...SOME SEVERE HAIL WILL ALSO BE POSSIBLE
WITH SEMI-DISCRETE STORMS IMMEDIATELY AHEAD OF THE SQUALL LINE.
..GUYER.. 09/08/2012
ATTN...WFO...LMK...OHX...HUN...PAH...MEG...LZK...
LAT...LON 34539361 35839150 38118866 38118722 36568681 34458857
34539361